In the medical field, various radioisotopes such as 131Cs, iodine-125, and palladium-103 are used for diagnostics and for treating various forms of cancer. For instance, 131Cs has been investigated for use in cancer research and treatments, such as in brachytherapy.
131Cs is a beta emitter and is produced by radioactive decay from neutron irradiated, naturally occurring barium-130 (“130Ba”). When irradiated, 130Ba captures a neutron, becoming 131Ba, which decays to 131Cs with an 11.5 day half-life. 131Cs decays to xenon-130 with a 9.7 day half-life. However, upon continued exposure to neutrons, 131Cs is converted to cesium-132 (“132Cs”) which is a gamma emitter.
To be effective in treating cancers, the 131Cs should be substantially pure, such as greater than approximately 99.9% 131Cs. For instance, the 131Cs should include substantially no impurities, such as 130Ba, 131Ba, or 132Cs. Conventional processes for producing 131Cs are time consuming, costly, and inefficient. As described in U.S. Pat. No. 7,479,261 to Bray et al., solid barium carbonate is irradiated in a nuclear reactor to produce a barium target. The irradiated barium carbonate target is removed from the nuclear reactor after 7-21 days to limit the formation of undesirable by-products, such as 132Cs. The irradiated barium carbonate target is stored for several days to limit exposure of personnel to the radiation, and then is dissolved in nitric acid to form a solution of cesium nitrate, barium nitrate, water, and carbon dioxide. The solution is concentrated to remove excess water, additional nitric acid is added, and the solution is dried to near dryness. The solution includes cesium nitrate, which is soluble in the nitric acid, and barium nitrate, which is insoluble in the nitric acid. The barium nitrate remaining in the solution is removed by precipitation. The cesium nitrate is separated from the barium nitrate by filtration or centrifugation. After removing the 131Cs and unwanted 132Cs, the irradiated barium carbonate target is stored to enable pure 131Cs to grow in. The process described above is then repeated periodically to recover the additional 131Cs. As such, multiple acts, which are time consuming and costly, are utilized in this process for producing and recovering the 131Cs from the irradiated barium carbonate target. In addition, the 9.7 day half-life of 131Cs provides significant decay loss of product in this multiple step process.
It would be desirable to produce and recover 131Cs of a high purity in a process including fewer acts and higher purity. It would also be desirable to eliminate the time, cost, and hazards to personnel associated with using a solid barium target.